Cranks

[Fingers]

I would guess it assumes the "bearing" doesn't crush or move?

You say the force concentration shows up at opposite end of crank from which the force is applied? Is this a steady state (analyzes one frame in time) or dynamic analysis (takes into account the actual movement & "records" some parameter(s) like stress, strain, deflection, movement, twist, etc? Is force concentration on oppopposite side of crank as applied load or same? i.e. crank is bowing (forces on same sides) or teetering (forces on opposing sides) about some axis?

Simulated bearing responds like a real bearing with a support factor. So there is some radial movement, but it is rated in pounds per inch displacement. Kinda like a very very stiff spring. Which is an accurate model of a real bearing.

This is steady state right now. You have to develop the states before you can move on to the dynamic and harmonic simulations.

 

[S Phinney]

Zero balance what? Talking harmonic dampeners here. What are YOU talking about.

Jon I think he us talking about a internally balanced engine with a neutral dampener and flywheel.

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[Fingers]

Ok. We do not have enough room to go totally internal balanced. I know a few have tried. You can get closer than we are now. Just can not make it work completely.


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[S Phinney]

Ok. We do not have enough room to go totally internal balanced. I know a few have tried. You can get closer than we are now. Just can not make it work completely.


Sent on the run from my Cell Phone

Jon several guys say they have completely internal balanced their cranks. Did you see the thread that Guy did with all the holes through the counter weights for some heavy metals? It cost a lot if money to do. Prices range from the best that I have seen of 1200 bucks and up to 2000 bucks for the metal. From what I have been told you almost always have to start with a crank that hasn't been balanced before because of them removing metal to balance it previously.

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[Dave c]

Jon several guys say they have completely internal balanced their cranks. Did you see the thread that Guy did with all the holes through the counter weights for some heavy metals? It cost a lot if money to do. Prices range from the best that I have seen of 1200 bucks and up to 2000 bucks for the metal. From what I have been told you almost always have to start with a crank that hasn't been balanced before because of them removing metal to balance it previously.

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Yes it can be done for sure. I saw NGM posted a picture a few months ago that there first 100% internal balance Dmax was done in 07' but wasent useing mallory, but a more heavy material. Looked like it took alot of metal though.

 

[Stingpuller]

Balance

Wade has a lot less bob weight with the aluminum rods and light pistons. That helps a bunch. He has also broken a crank or two with his special cams and nasa spec assembly.

 

[juddski88]

http://www.enginelabs.com/engine-te...-of-ati-performance-explains-damper-dynamics/

Figured I'd share this here for those who may not have followed some of the lingo being used

 

[Fingers]

Lets not confuse internally balanced cranks with just inside the crankcase balanced cranks. A truely internally balanced crank has near equal size counter weights across the entire crank. Externally puts the heavier masses to either end of the crank.

 

[Dave c]

Lets not confuse internally balanced cranks with just inside the crankcase balanced cranks. A truely internally balanced crank has near equal size counter weights across the entire crank. Externally puts the heavier masses to either end of the crank.

Not exactly true, external is exactly that, external of the counterweights! Balanced by the balancer and flywheel mostly along with some crank drilling.

Internal is JUST in the counter weights being modified, actually, it doesent even use the flywheel or the balancer during the balance process at all. Counter weights, may not all be the same due to many variables. But the balance machine can deside on that.

http://www.eaglerod.com/index.php?option=com_content&task=view&id=27&Itemid=25

 

[Yellow Jacket]

My SoCal done "internally" balanced stock crank has 5 pieces of heavy metal in the front counterweight and 5 in the rear counterweight and 4 pieces in the second counterweight and second to last counterweight... No counterweight on the balancer or flywheel.

This is how I see it, but I'm not an engineer or engine machine shop or builder... I would think an equal number of slugs in each counterweight would be best, but either is internally balanced from how I understand it...

 

[S Phinney]

Lets not confuse internally balanced cranks with just inside the crankcase balanced cranks. A truely internally balanced crank has near equal size counter weights across the entire crank. Externally puts the heavier masses to either end of the crank.

I would say possibly near equal counterweight weights but not necessarily the size itself. It does not consider balancer or flywheel while balancing the crank. Only bob weights are considered. then the Balancer and flwheel are neutral balanced and don't require the offset weights on them.

 

[juddski88]

My SoCal done "internally" balanced stock crank has 5 pieces of heavy metal in the front counterweight and 5 in the rear counterweight and 4 pieces in the second counterweight and second to last counterweight... No counterweight on the balancer or flywheel.

This is how I see it, but I'm not an engineer or engine machine shop or builder... I would think an equal number of slugs in each counterweight would be best, but either is internally balanced from how I understand it...

I'm no expert either, but its not that simple. I'm guessing because of the differences in mass and placement of which, of each counterweight.

 

[LtEng5]

sub'd.....

 

[Fahlin Racing]

:thumb: Good reading

 

[Fingers]

Need a little help. I could use some more pictures of the breaks and in particular, I want to see if the witness marks shown in the attachment line up with the break.

These marks are outside where the bearing should be riding and are on the fillet radius itself. They are typified by the unworn or polished band between them and the contact area of the bearing itself.

It would be great if you can post a picture the shows the intersection of the witness mark and the initiation point of the break.

 

[Burn Down]

 

[Bigdirtylbz07]

I will gladly send the parts of my broken crank to whoever wants it for inspecting it


Sent from a truck somewhere in the US

 

[Fingers]

Removed

 

[Fingers]

On close examination, I see there IS a rub that lines up exactly with the break.

Hmmm. Don't know if it is the cause, but I will be looking more closely into it.

 

[Burn Down]

On close examination, I see there IS a rub that lines up exactly with the break.

Hmmm. Don't know if it is the cause, but I will be looking more closely into it.

Which rub? The break initiates square in the middle of the journal, at the fillet, and just above the shiny lower rub ring.

Does your program show a higher load on the #2 rod journal?